Double-walled ultra-high vacuum vessel defining a work chamber



Dec. 28, 1965 G. KIENEL ET AL 3,226,467

DOUBLE-WALLED ULTRA-HIGH VACUUM VESSEL DEFINING A WORK CHAMBER FiledSept. 27, 1961 2 Sheets-Sheet 1 O -/'\-M s 1 K) H l5 l6 2 f 56 4 I" 2223 lo 25 7 9 N 26- I as x 34 f FIG. 2 32 40 5a i i FIG. 3 33 3'INVENTORS GERHARD KIENEL 2 BY FRIEDRICH ELSASSER lum PM ATTORNEYS Dec.28, 1965 G. KIENEL ET AL 3,226,467

DOUBLE-WALLED ULTRA-HIGH VACUUM VESSEL DEFINING A WORK CHAMBER FiledSept. 27, 1961 2 Sheets-Sheet 2 VII/53%| INVENTORS GERHARD KIENELFRIEDRICH ELSASSER Kb/sum M ATTORNEYS United States Patent 3,226,467DOUBLE-WALLED ULTRA-HIGH VACUUM v VESSEL DEFINING A WGRK QHAIVEERGerhard Kienel, Hanan (Main), and Friedrich Elsasser, Langenselbold,near Hanan (Main), Germany, assignors to W. C. Heracus G.m.b.H., Hanan(Main), Germany, a firm of Germany Filed Sept. 27, 1961, Ser. No.141,053 Claims priority, application Germany, Sept. 28, 1960, H 36,080,Patent 1,829,431, H 36,083, Patent 1,829,478; Sept. 29, 1960, H 36,084,Patent 1,829,479

11 Claims. (Cl. 174-18) The present invention relates to double-walledultrahigh vacuum vessels and to means for operating the same.

For operations and investigations in nuclear and vacuum engineering andthe like which are to be carried out under a high vacuum it is known forsome time to employ an apparatus in which the actual evacuated workchamber is surrounded by a protective chamber which is likewiseevacuated, but independently of the work chamber. The amount of gaseswhich might enter the work chamber through small leakages in the wallsthereof may thus be reduced so considerably that an extremely highvacuum may be attained in the work chamber with a reasonable amount ofpumping energy and within a short length of time. The expressionultra-high vacuum as used herein is supposed to mean pressures as low asabout 10- mm. Hg and less. The vacuum which is produced in theprotective chamber is usually a high vacuum, that is, one of at least1() mm. Hg and preferably one as low as 10- mm. Hg or less. Theevacuation of the protective chamber is carried out by conventionalmeans, for example, by a mechanical backing pump and by a diffusionpump.

A similar pump unit may also be employed for evacuating the workchamber, although it is then necessary to provide suitable means forpreventing a back-diffusion of the fuel vapors of the diffusion pump.These means consist, for example, of several bafiles, the last of whichis located immediately in front of the work chamber and is maintained ata very low temperature, for example, of 150 C. It is, however, alsopossible to employ for this purpose the conventional getter ion umps orkryo-pumps which produce an ultra-high vacuum which is free of oilvapors.

For the production and maintenance of an ultra-high vacuum it is ofextreme importance to prevent as much as possible the liberation of anygases and even the smallest amounts thereof. The reason for this will beevident from the following considerations:

Under atmospheric pressure, that is, at about 760 mm. Hg, one cubicmeter of air contains 1.2 kg. of gas, while at a pressure of mm. Hg itonly contains 10- mg. of gas which originally, that is, underatmospheric pressure, had a volume of only mm Even such extremely smallamounts of gases when liberated may therefore increase the originalpressure to twice its value. Such gases may be liberated, for example,from the walls of the vacuum vessel, from the materials to be treated inthis vessel, and from other sources.

In order to prevent as much as possible a subsequent liberation of gasesfrom the walls of the work chamber it is conventional for some time toheat or bake out these walls prior to the formation of the ultra-highvacuum. Such heating is usually carried out electrically, that is,either by induction or resistance. Since these walls lie between thework chamber which is maintained under an ultra-high vacuum and thesurrounding protective chamber which is likewise maintained under a highvacuum, they are subjected to hardly any stresses and may therefore bemade very thin. The walls themselves may therefore be used as electricresistance elements and be heated very easily and economically.

Although the above-mentioned problems are wellknown in the art and someof them have been adequately solved for some time, there is a series ofquestions which have as yet not been solved satisfactorily. Ultra-highvacuum apparatus are employed primarily for carrying out physical andother investigations and processes, for example, for examining verypure, gas-free surfaces, for certain evaporation processes, for use inconnection with nuclear physics apparatus, such as accelerators, etc. Itis also often advisable or even necessary to observe the proceedingsoccurring within the vacuum apparatus, to control electrical proceedingstherein, or to move certain elements within the apparatus while it is inoperation. For this reason, such apparatus are usually provided withinspection windows and with electrical lead-ins and lead-ins fortransmitting mechanical movements into the apparatus.

Such devices have been applied for a long time in vacuum apparatus witha single wall, that is, without an evacuated protective chambersurrounding the work chamber. The inspection windows of theseconventional vacuum apparatus usually consist of glass panes which aresealed around their edges by packings of an elastic material. Forlead-ins for movable mechanical elements and for electric conductors,bolted sealing means with packings of elastic materials, for example,shaft sealing rings, are mostly used. Such materials can, however, notbe used for ultra-high vacuum apparatus since all of them without anyexception have a vapor pressure which is considerably higher than thedesired vacuum.

Tightly bolted, cemented, and other solidly mounted sealing means canalso be applied in double-walled vacuum apparatus only with difficultysince they must be firmly connected to the walls into which they areinserted. They are therefore secured not only to the thicker outer wallof the protective chamber, but also to the usually thinner wall of thework chamber. This involves a series of difiiculties. First, the lead-inapertures in the two walls must be in accurate alignment with eachother. Second, by tightly bolting the sealing means to the thin wall ofthe work chamber, the latter may easily be deformed. Furthermore, it isvery difiicult to carry out the necessary assembly work between the twowalls and, last but not least, any exchange of such packing meansrequires a very great amount of time and effort.

7 The same also applies to cementing or to metallic packings which mustalways be properly molded to attain a proper sealing effect.

It is an object of the present invention to over-come all of thesedisadvantages by the provision of very simple and effective means. Theinvention concerns a double-walled ultra-high vacuum vessel with anouter wall which is capable of resisting the outer atmospheric pressureand forms the outer wall of a protective chamber which may be highlyevacuated, and with an inner wall which separates the protective chamberfrom an inner work chamber in which the desired ultra-high vacuum may beproduced. The invention further concerns the provision of such adouble-walled ultra-high vacuum vessel with one or more devices fortransmitting mechanical movements or electric currents and potentialsfrom the outside through both walls into the work chamber, and forpermitting an inspection of the closed work chamber from the outside. Incombination with such an apparatus and with such devices the inventionfurther resides in sealing these devices in the outer wall by theemployment of suitable sealing means which are conventional as such andmay consist of solid or elastic sealing means, for example, elasticsealing rings, packings, 'shaft sealing rings, bellows, metallic sealingmeans which are bolted and thereby deformed, or the like. The inventionfurther consists in sealing such devices in the inner wall by means offree, narrow gaps which are open at both ends and have :a length of atleast 10 mm.

The objects, features, and advantages of the present invention willbecome more clearly apparent from the following detailed detaileddescription thereof which is to be read with reference to theaccompanying drawings, in which:

FIGURE 1 shows a diagrammatic cross section of a double-walled vacuumapparatus according to the invention;

FIGURE 2 shows an enlarged cross section of a part of the apparatusaccording to FIGURE 1 with a lead-in for mechanically transmitting arotary movement to the inside of the apparatus;

FIGURE 3 shows a view of a part of the apparatus similar to FIGURE 2with a lead-in for mechanically transmitting a reciprocating movement tothe inside of the apparatus;

FIGURE 4 shows another view similar to FIGURES 2 and 3 with a lead-infor conducting electric currents of different potentials but usually oflow amperages into the apparatus;

FIGURE 5 shows a further view similar to FIG- URES 2 to 4 with a lead-infor conducting a strong electric current of a single potential into theapparatus; while FIGURE 6 shows an enlarged cross section of theinspection window of the apparatus.

In the drawings, FIGURE 1 shows a general view of the entire vacuumapparatus according to the invention, while FIGURES 2 to 6 show specificfeatures and modifications thereof. The work chamber 1 of the vacuumapparatus which is maintained under an ultra-high vacuum is defined by awall 2 which is usually relatively thin and is, in turn, surrounded by aprotective chamber 3 which is likewise evacuated and closed toward theouter atmosphere by a thicker outer wall 4 of a sufficient mechanicalresistance.

The protective chamber 3 is limited at its rear side, that is, at theright side of FIGURE 1, by an oval bottom 5 surrounded by the atmosphere5a which is welded is to the cylindrical outer wall 4, while at thefront side it is provided with a cover 6 which may be closed by a lock 7and may be opened by pivoting about a hinge 8. A vacuum-tight closure ofchamber 3 is attained, for example, by a sealing ring 9 which isinserted between the flanges on wall 4 and the cover 6. Chamber 3 may beevacuated in a conventional manner through a vacuum line 10 to a vacuumof 10- to 10* mm. Hg by means of a pump unit 11. The outer wall 4 issupported by a frame, not shown.

The relatively thin inner wall 2 between the protective chamber 3 andthe work chamber 1 is likewise closed at the rear side by a bottom whichis integrally secured to wall 2. At the front side, wall 2 carries acover 16 which may be closed by a lock 17 and may be opened by pivotingabout a hinge 18. Work chamber 1 is mounted in the protective chamber 3on supports 19 which are preferably insulated relative to the outer wall4. Near its outer ends the cylindrical part of wall 2 carries contactrings 20 to which an electric current may be supplied through theconductors 21 which pass through sealed lead-in insulators 22 toconnecting terminals 23 at the outside. From a suitable source, notshown, an electric current, preferably alternating current, may besupplied to terminals 23 so as to heat the cylindrical part of wall 2 toa temperature of, for example, 450 C., whereby this wall will be freedof any adsorbed or occluded gases. A vacuum line 25 passes from workchamber 1 through the outer wall 4 to a pump unit 26 which is capable ofproducing the desired ultrahigh vacuum of, for example, 10- or an evenhigher vacuum within work chamber 1. The vacuum pump units may be of thetype as mentioned in the beginning. They as well as their dimensions andoperation are so conventional that they do not need to be furtherdescribed here- The present invention concerns primarily the provisionof suitable sealing means for the lead-ins M for transmitting mechanicalmovements to the inside of work chamber 1, as illustrated in detail inFIGURES 2 and 3, for electrical lead-ins E, as illustrated in FIGURES 4and 5, and for the inspection windows W, as illustrated in FIG- URE 6.The difiiculties which are mentioned in the beginning and which areovercome by the present invention are also due to the fact that theselead-ins and windows pass through or are mounted in the walls of bothvessels of the vacuum apparatus and must be designed so as not only toinsure for a long time a tight and reliable sealing effect but also topermit an easy installation and repair thereof.

As illustrated in FIGURE 2, for installing the lead-in M according toFIGURE 1, the outer wall 4 is provided with a bore 30 through which arotatable shaft 31 extends which is sealed by a sealing ring 32, theouter part 33 of which is clamped by screws 34 between a fitting 35 andwall 4, while the inner part 36 thereof which is preferably providedwith a spring 37 engages with shaft 31. The inside of sealing ring 32 isevacuated through bore 30 toward theprotective chamber 3. If therotatable shaft 31 is designed as illustrated in FIGURE 2, it may alsobe slidable to some extent in the longitudinal direction to transmitlongitudinal movements to the inside of work chamber 1. If, however,such longitudinal movements should be prevented, shaft 31 may beprovided with one or more shoulders, flanges, or the like.

As shown in FIGURE 2, the diameter of the inwardly extending part 38 ofshaft 31 is preferably slightly reduced and passes through a bore 39 inthe inner wall 2 and through a bushing 40 thereon into work chamber 1.The length of this bushing including the thickness of wall 2 preferablyamounts to at least 10 mm. Within bore 39 and bushing 40 the shaftportion 38 is surrounded by a tube 41 which is made of a material whichdoes not release any gases, such as glass, molten quartz, gastightceramics, or the like. This tube 41 considerably reduces the friction onthe inner lead-in which is exposed to a high vacuum. Tube 41 which is ofa greaterlength than that of bushing 40 including the thickness of wall2, and thus projects therefrom, passes freely, that is, without anydeformable sealing means, through bore 39 and bushing 40 and it isseparated therefrom only by narrow annular spacing or diffusion gaps ofa considerable length.

The lead-in sealing arrangement according to FIGURE 3 differs from thataccording to FIGURE 2 only insofar as a resilient member in the form ofa corrugated tube or bellows 45 and a spline 46 on shaft 31 only permitthe shaft to move in the longitudinal direction. The corrugated tube 45is soldered at one end to a collar 47 on shaft 31, while its other endis secured to a plate 48 which is clamped by screws 34 to the wall 4between a fitting in the form of a ring 49 and an outer sealing disk 50and an inner rubber-ring 51. The inside of the corrugated tube 45communicates through bore 30 with the vacuum in the protective chamber 3and it may be reinforced against pressure by the insertion of coilsprings or the like.

If tube 41 is made of a suitable material, preferably of molten quartz,shaft 38 will remain movable through the lead-in according to theinvention even though wall 2 of work chamber 1 is heated to highertemperature, for example, to 450 C. Naturally, the inner diameter oftube 41 must then be made of a size to allow for the thermal expansionof shaft 31. As previously mentioned, when the walls of work chamber 1are thus heated, they will be freed of any adhering, adsorbed oroccluded gases to such an extent that a very high vacuum may be producedin the work chamber within a very short time.

FIGURE 4 illustrates an electric lead-in which is very similar to theshaft lead-in according to FIGURES 2 and 3. The outer wall 4 is againprovided with a bore 30 which is in axial alignment with the centralbore 52 of a fitting 53 which is secured by screws 34 to wall 4 andclamps a sealing disk 50 and a rubber ring 51 similarly as in FIGURE 3tightly against wall 4. Fitting 53 has a tubular extension 54 on theouter end of which a small terminal box 55 is mounted. The outer wall 56of terminal box 55 is provided with bores 57 through which electricconductors 58 are passed. These conductors are insulated from wall 56and are secured gastight thereto by glass insulators 59 which are fusedto the conductors and to wall 56. Conductors 58 then pass through aninsulating tube 60 of plastic, ceramics, glass, quartz, or the likewhich is loosely inserted into bores 52 and 30 so that the vacuum inchamber 3 also extends into the terminal box 55.

Again similarly as in FIGURES 2 and 3, wall 2 of work chamber 1 has abore 39 and it also carries on its inner side a bushing 40 of the sameinner diameter as and coaxially with bore 39. Bore 39 and bushing 40contain an insulating tube 61 which is made of a material which does notgive off any gases such as glass, molten quartz, gastight ceramics, orthe like, and which encloses the conductors 58 leading into workchamber 1. Similarly as tube 41 in FIGURES 2 and 3, insulating tube 61passes freely, that is, without any deformable sealing means throughbore 39 and bushing 40 so as only to leave nar row diffusion gaps whichshould be of a considerable length, that is, at least mm. The conductors58 are also passed through insulating tubes 60 and 61 so as to leavesimilar diifusion gaps therein.

The separation of insulating tubes 60 and 61 to form two parts has theadvantage that bores 30 and 34 do not have to be as accurately alignedas it is necessary for a shaft lead-in as shown in FIGURES 2 and 3. Theindividual parts of the lead-in may therefore be more easily assembledrelative to each other.

Whereas the electric lead-in according to FIGURE 4 contains two or moreconductors, for example, for conducting electric currents of severaldfferent but relatively low potentials into the work chamber 1, FIGURE 5illustrates another electric lead-in for a single conductor 62 forconducting a strong current of one potential into the work chamber 1.Since this conductor 62 has a shaftlike thickness which depends upon thestrength of the current to be conducted, the lead-in is designed similarto the shaft lead-ins according to FIGURES 2 and 3, except that it ismore simple since the conductor 62 does not have to be movable like theshafts 31 in FIGURES 2 and 3. Conductor 62 is therefore rigidly securedto the fitting 63 which may also serve as a connecting terminal. In thisevent not only the conductor 62 but the fitting 63 as well are made of ahighly conductive material, such as copper or the like. The sealing disk64 which together with a rubber ring 65 is inserted between fitting 63and. wall 4 should in this case consist of a suitable insulatingmaterial, and screws 34 which secure fitting 63 to wall 4 and clamp thesealing disk 64 thereon are also insulated from fitting 63 by insulatingbushings 66.

The other features and parts of this lead-in are similar to those asdescribed with reference to FIGURES 2 and 3 and are therefore identifiedby the same numerals. Tube 41 which is preferably made of molten quartzalso has the purpose of electrically insulating the conductor 62 fromwall 2 of the work chamber.

FIGURE 6 illustrates the application of the inventive sealing means tothe inspection windows as shown at W in FIGURE 1. A window frame with anopening 71 is inserted into an aperture in a part of the outer wall 4 ofchamber 3, for example, in the cover 6 as shown in FIGURE 1. The glassor quartz pane 72 is clamped by a mounting ring 73 and by screws 74against a sealing disk 75 and a rubber ring 76 on frame 70. The numberof screws 74 to be used depends upon the size of the window. After theprotective chamber 3 has been evacuated, the glass or quartz pane 72will be pressed by the outer atmospheric pressure against the sealingdisk 75 and will thus be tightly sealed relative to the inside ofchamber 3.

The inner wall 2 which forms the wall of work chamber 1 also has anaperture into which another window frame 77 with an opening 78 isinserted. The window pane 79 is merely held in its proper position onwindow frame 77 by means of another mounting ring 80 and screws 81, anddoes not require any special sealing means nor to be clamped tightlybetween frame 77 and. ring 80. Screws 81 only need to be tightened tosuch an extent that the edge portion of pane 79 engages flatly againstframe 77. When the protective chamber 3 and the work chamber 1 are bothevacuated, the forces occurring within the two chambers will be so smallthat practically no mechanical stresses will act upon the window pane 79and the pane will not be pressed against the window frame 77 with such aforce that it will be endangered.

The edge portion of window pane 79 which engages with the window frame77 has a width of approximately 10 mm. Since the surfaces of both partsare not partic ularly finished and especially their engaging surfacesare not ground in accordance with each other, there will be narrow gaps81 between them which serve as diffusion gaps similarly to the gaps 39as described with reference to FIGURES l to 5.

The lead-in, inspection, and sealing means according to the inventionpreferably have the followng dimensions:

In the mechanical lead-ins according to FIGURES 2 and 3 and also in theelectric lead-ins according to FIG- URE 5, the reduced shaft orconductor portion extending through the inner wall 2 has a diameter ofabout 12 mm. The inner diameter of quartz tube 41 which is slipped overthis portion is at least 0.05 mm. but not more than 0.2 mm. greater thanthe diameter of this reduced portion. The wall thickness of quartz tube41 amounts to about 2 mm. Gap 39 also has a width of at least 0.05 mm.and not more than 0.2 mm. Therefore, the inner diameter of bushing 40amounts to about 16 mm.

Although the lead-in through the inner wall has thus relatively largegaps which ordinarily would result in a serious leakage of pressure andwould thus prevent the formation and maintenance of a very high vacuumin Work chamber 1, these gaps result in the present case in a very goodsealing effect since the protective chamber 3 also contains a very highvacuum and since the free path of the molecules then amounts to at least5 cm. at about 10 mm. Hg, but generally to considerably more, forexample, to about 50 cm. at 101, mm. Hg.

Although our invention has been illustrated and described with referenceto the preferred embodiments thereof, we wish to have it understood thatit is in no way limited to the details of such embodiments, but iscapable of numerous modifications within the scope of the appendedclaims.

Having thus fully disclosed our invention, what we claim is:

1. In an ultra-high vacuum vessel for reactions and the like in a gasfree area having an outer wall housing adapted to resist the outeratmospheric pressure, an inner wall defining an interior work chamberand spaced from said outer wall, said outer and inner walls defining aprotective chamber surrounding said work chamber, independent conduitmeans for separately connecting said work chamber and said protectivechamber to at least one pump unit for evacuating said work chamber to anultrahigh vacuum and said protective chamber to a high vacuum, saidouter and inner walls having respective apertures substantially inalignment with each other, said apertures being of substantially thesame area, means extending through at least one pair of said alignedapertures in said Walls for transmitting energy from the outside intosaid work chamber, and mechanical sealing means for sealing said energytransmitting means relative to said outer wall, means extending throughsaid inner wall aperture spaced from the aperture wall and extendingsubstantially on veach side of the inner Wall, said energy-transmittingmeans extending through said last named means in the aperture in saidinner wall in a manner so as to leave a free narrow gap connecting saidwork and protective chambers, said gap having a considerable length andforming a difiusion gap for substantially sealing said work chamberrelative to said protective chamber.

2. In an ultra-high vacuum vessel for reactions and the like in a gasfree area having an outer wall adapted to resist the outer atmospherepressure, an inner wall defining a work chamber and spaced from saidouter wall, to form an evacuable area therebetween, said outer and innerwalls defining a protective chamber surrounding said work chamber, atleast one pump unit for evacuating said work chamber to a high vacuum,independent connection means for separately connecting said work chamberand said protective chamber to said respective pumps, said outer andinner walls having conforming apertures substantially in alignment witheach other, interconnecting means extending through at least one pair ofsaid aligned apertures in said walls for transmitting energy from theoutside into said work chamber, aligned outer and inner inspectionwindows connected to the wall portions surrounding at least one otherpair of said aligned apertures, and mechanical sealing means in eachchamber wall for separately sealing said energy transmitting means andsaid outer inspection window to said outer wall, means extending throughsaid inner wall aperture spaced from the aperture wall and extendingsubstantially on each side of the inner wall, said energy transmittingmeans extending through said last named means in the aperture in saidinner wall and the inner inspection window being connected to said innerwall in a manner so as to leave free narrow gaps connecting said workand protective chambers and each having a considerable length andforming a diffusion gap for substantially sealing said work chamberrelative to said protective chamber.

3. In an ultra-high vacuum vessel for reactions and the like in a gasfree area having an outer wall adapted to resist the outer atmosphericpressure, an inner wall defining a work chamber and spaced from saidouter wall, said outer and inner walls defining a protective chambersurrounding said work chamber, means for separately connecting said workchamber and said protective chamber to at least one pump unit forevacuating said work chamber to an ultra-high vacuum and said protectivechamber to a high vacuum, said outer and inner walls having aperturessubstantially in alignment with each other for permitting the operationof reactions in the inner chamber, means extending through at least onepair of said aligned apertures in said walls for transmitting electricalenergy from the outside into said work chamber, outer and innerinspection windows secured to the wall portions surrounding at least oneother pair of said aligned apertures, mechanical sealing means -forseparately sealing said energy transmitting means and said outerinspection window to said outer wall, and means for connecting saidinner inspection window without sealing means to said inner wall, meansextending through said inner wall aperture spaced from the aperture walland extending substantially on each side of the inner wall, said energytransmitting means extending through said last named means in theaperture in said inner Wall and said inner inspection window beingconnected to said inner wall in a manner so as to leave free narrow gapsconnecting said work and pro tective chambers and each having aconsiderable length and forming a diffusion gap for substantiallysealing said work chamber relative to said protective chamber.

4. In an ultra-high vacuum vessel for reactions and the like in a gasfree area having an outer wall adapted to resist the outer atmosphericpressure, an inner wall defining a work chamber and spaced from saidouter wall, said outer and inner walls defining a protective chambersurrounding said work chamber, means for separately connecting said workchamber and said protective chamber to at least one pump unit forevacuating said work chamber to an ultra-high vacuum and said protectivechamber to a high vacuum, said outer and inner Walls having aperturessubstantially in alignment with each other, means extending through atleast one pair of said aligned apertures in said walls for transmittingenergy from the outside into said work chamber, and mechanical sealingmeans for sealing said energy-transmitting means relative to said outerwall, means extending through said innerwall aperture spaced from theaperture wall and extending substantially on each side of the innerwall, said energy-transmitting means extending through said last namedmeans in the aperture in said inner Wall in a manner so as to leave afree narrow gap connecting said work and protective chambers, said gaphaving a considerable length and forming a dilfusion gap forsubstantially sealing said work chamber relative to said protectivechamber.

5. In an ultra-high vacuum vessel for reactions and the like in a gasfree area having an outer wall adapted to resist the outer atmosphericpressure, an inner wall defining a work chamber and spaced from saidouter wall, said outer and inner walls defining a protective chambersurrounding said work chamber, means for separately connecting said workchamber and said protective chamber to at least one pump unit forevacuating said work chamber to an ultra-high vacuum and said protectivechamber to a high vacuum, said outer and inner walls having aperturessubstantially in alignment with each other, means extending through atleast one pair of said aligned apertures in said walls for transmittingenergy from the outside into said work chamber and leaving a free narrowgap connecting said work and protective chambers, outer and innerinspection windows secured to the wall portions surrounding at least oneother pair of said aligned apertures, mechanical sealing means forseparately sealing said energy-transmitting means and said outerinspection window to said outer wall, means extending through said freenarrow gap spaced from the aperture wall and extending substantially oneach side of the inner wall, said energy transmitting means extendingtherethrough, and means for connecting said inner inspection windowwithout sealing means to said inner wall, said gap having a considerablelength and forming a diffusion gap for substantially sealing said workchamber relative to said protective chamber.

6. In an ultra-high vacuum vessel for reactions and the like in a gasfree area having an outer wall adapted to resist the outer atmosphericpressure, an inner wall defining a work chamber and spaced from saidouter wall, said outer and inner walls defining a protective chambersurrounding said work chamber, means for separately connecting said workchamber and said protective chamber to at least one pump unit forevacuating said work chamber to an ultra-high vacuum and said protectivechamber to a high vacuum, said outer and inner Walls having aperturessubstantially in alignment with each other, a tubular member secured tosaid inner wall in alignment with said aperture therein, means extendingthrough at least one pair of said aligned apertures in said walls andthrough said tubular member for transmitting energy from the outsideinto said work chamber, and mechanical sealing means for sealing saidenergy-transmitting means relative to said outer wall, saidenergy-transmitting means extending through said aperture in said innerwall and through said tubular member in a manner so as to leave a freenarrow gap connecting said work and protective chambers, said gap havinga considerable length and forming a diffusion gap for substantiallysealing said work chamber relative to said protective chamber.

7. In an ultra-high vacuum vessel for reactions and the like in a gassfree area having an outer Wall adapted to resist the outer atmosphericpressure, an inner wall defining a work chamber and spaced from saidouter wall, said outer and inner Walls defining a protective chambersurrounding said work chamber, and having a relatively higher pressurethan the inner chamber means for separately connecting said work chamberand said protective chamber to at least one pump unit for evacuatingsaid work chamber to an ultra-high vacuum and said protective chamber toa high vacuum, said outer and inner walls having apertures substantiallyin alignment with each other and of substantially equal dimensions, atubular member secured to said inner wall in alignment with saidaperture therein, a quartz tube loosely extending through the bore ofsaid tubular member, means extending through at least one pair of saidaligned apertures in said walls and through said quartz tube fortransmitting electrical energy from the outside into said work chamber,and mechanical sealing means for sealing said energytransmitting meansrelative to said outer wall, said energy-transmitting means extendingthrough said aperture in said inner wall and said quartz tube in amanner so as to leave a free narrow gap connecting said work andprotective chambers, said gap having a considerable length and forming adiffusion gap for substantially sealing said work chamber relative tosaid protective chamber.

8. In an ultra-high vacuum vessel for recations and the like in a gasfree area having an outer wall adapted to resist the outer atmosphericpressure, an inner wall defining a work chamber and spaced from saidouter wall, said outer and inner walls defining a protective chambersurrounding said work chamber, means for separately connecting said workchamber and said pro tective chamber to at least one pump unit forevacuating said work chamber to an ultra-high vacuum and said protectivechamber to a high vacuum, said outer and inner walls having aperturessubstantially in alignment with each other, a tubular member secured tosaid inner wall in alignment with said aperture therein, a quartz tubeloosely extending through the bore of said tubular member, a rotatableshaft extending from the outside atmosphere through one pair of saidaligned apertures in said walls and through said quartz tube into saidwork chamber, and at least one shaft sealing ring slidably connected tosaid shaft and secured to said outer wall for sealing said shaftrelative to said outer wall, said shaft extending through said aperaturein said inner wall and said quartz tube in such a manner so as to leavea free narrow gap connecting said work and protective chambers, said gaphaving a relatively considerable length and forming a diffusion gap forsubstantially sealing said Work chamber relative to said protectivechamber.

9. In an ultra-high vacuum vessel for reactions in vacuo having an outerwall adapted to resist the outer atmospheric pressure, an inner walldefining a work chamher and spaced from said outer wall, said outer andinner walls defining a protective chamber area surrounding said Workchamber, conduit means for separately connecting said work chamber andsaid protective chamber to at least one pump unit for evacuating saidwork chamber to an ultra-high vacuum and said protective chamber to ahigh vacuum said outer and inner walls having apertures substantially inalignment with each other, a tubular member secured to said inner wallin alignment with said aperture the-rein, a quartz tube looselyextending through the bore of said tubular member from the outer to theinner chamber, a shaft adapted to reciprocate in its longitudinaldirection and extending from the outside through one pair of saidaligned apertures in said walls and through said quartz tube into saidwork chamber, a metallic corrugated resilient seal-ing member secured atone end to said shaft, at least one elastic sealing ring interposedbetween the other end of said metallic sealing member and said outerwall, and means for securing said other end and said sealing ring inseal-ing engagement to said outer wall, said shaft extending throughsaid aperture in said inner wall and said quartz tube in such a mannerso as to leave a free narrow gap connecting said work and protectivechambers, said gap having a relatively considerable length and forming adiffusion gap for substantially sealing said work chamber relative tosaid protective chamber.

10. In an ultra-high vacuum vessel for manipulating reactions thereinunder gas free conditions having an outer wall adapted to resist theouter atmospheric pressure, an

inner wall defining a Work chamber and spaced from said outer wall, saidouter and inner walls defining a protective chamber surrounding saidwork chamber, conduit means for separately connecting said work chamberand said protective chamber to at least one pump unit for evacuatingsaid work chamber to an ultra-high vacuum and said protective chamber toa high vacuum, said outer and inner walls having apertures substantiallyin alignment with each other, a tubular member secured to said innerwall in alignment with said aperture therein, a quartz tube looselyextending through the bore of said tubular member to said work chamber,at least one electrio conductor extending from the outside of the outerwall through one pair of said aligned apertures in said Walls butwithout engaging with said walls, and through said quartz tube into saidwork chamber, and elastic insulating sealing means connecting saidconductor to said outer Wall, said conductor extending through saidaperture in said inner wall and said quartz tube in a manner so as toleave a free narrow gap connecting said work and protective chambers,said gap having a relatively considerable length and forming a diffusiongap for substantially sealing said work chamber relative to saidprotective chamber.

11. In an ultra-high vacuum vessel used for reactions therein having anouter wall adapted to resist the outer atmospheric pressure, an innerwall defining a work chamber and spaced from said outer wall, said outerand inner walls defining a protective chamber surrounding said workchamber, conduit means for separately connecting said work chamber andsaid protective chamber to at least one pump unit for evacuating saidwork chamber to an ultrahigh vacuum and said protective chamber to ahigh vacuum respectively, said outer and inner walls having aperturessubstantially in alignment with each other, a tubular member secured tosaid inner wall in alignment with said aperture therein and extendinginto said work chamber, a quartz tube loosely extending through the boreof said tubular member and having several leadin passages therein, alead-in container hermetically closed toward the outside, elasticsealing means interposed between said container and said outer wall,means for securing said leadin container to said outer wall so as to besealed to said outer wall by said sealing means, at least two electricconductors extending from the outside through said lead-in container,said outer and said inner walls without engaging with said walls, andthrough said passages in said quartz tube into said work chamber in amanner so as to leave a free narrow gap connecting said work andprotective chambers, said gap being of considerable length and forming adiffusion gap for substan- 11 12 tially sealing said work chamberrelative to said protective OTHER REFERENCES chamber and insulatingmeans for insulating said concome: A High Vacuum Seal, pubhshed 1nReview ductors from said container and sald outer Wall. ScientificInstruments, v01. 15 No. 2 February 1944,

References Cited by the Examiner 5 46 and 47 Tehed Knight: VacuumFeed-Through Bushing, IBM Tech- UNITED STATES PATENTS nical DisclosureBulletin, v01. 2, N0. 4, December 1959. 679,898 8/1901 Jesse 74-1821,041,485 1 9 s r 27753 X JOHN F. BURNS, Primary Examiner, 2,144,5581/1939 Bahls 174151 2 439 30 4/1943 Heinemam 10 JOHN P. WILDMAN,Examiner.

3,018,561 1/1962 Wells

1. IN AN ULTRA-HIGH VACUUM VESSEL FOR REACTIONS AND THE LIKE IN A GASFREE AREA HAVING AN OUTER WALL HOUSING ADAPTED TO RESIST THE OUTERATMOSPHERIC PRESSURE, AN INNER WALL DEFINING AN INTERIOR WORK CHAMBERAND SPACED FROM SAID OUTER WALL, SAID OUTER AND INNER WALLS DEFINING APROTECTIVE CHAMBER SURROUNDING SAID WORK CHAMBER, INDEPENDENT CONDUITMEANS FOR SEPARATELY CONNECTING SAID WORK CHAMBER AND SAID PROTECTIVECHAMBER TO AT LEAST ONE PUMP UNIT FOR EVACUATING SAID WORK CHAMBER TO ANULTRHIGH VACUUM AND SAID PROTECTIVE CHAMBER TO A HIGH VACUUM, SAID OUTERAND INNER WALL HAVING RESPECTIVE APERTURES SUBSTANTIALLY IN ALIGNMENTWITH EACH OTHER, SAID APERTURES BEING OF SUBSTANTIALLY THE SAME AREA,MEANS EXTENDING THROUGH AT LEAST ONE PAIR OF SAID ALIGNED APERTURES INSAID WALLS FOR TRANSMITTING ENERGY FROM THE OUTSIDE INTO SAID WORKCHAMBER, AND MECHANICAL SEALING MEANS FOR SEALING SAID ENERGYTRANSMITTING MEANS RELATIVE TO SAID OUTER WALL, MEANS EXTENDING THROUGHSAID INNER WALL APERTURE SPACED FROM THEAPERTURE WALL AND EXTENDINGSUBSTANTIALLY ON EACH SIDE OF THE INNER WALL, SAID ENERGY-TRANSMITTINGMEANS EXTENDING THROUGH SAID LAST NAMED MEANS IN THE APERTURE IN SAIDINNER WALL IN A MANNER SO AS TO LEAVE A FREE NARROW GAP CONNECTING SAIDWORK AND PROTECTIVE CHAMBERS, SAID GAP HAVING A CONSIDERABLE LENGTH ANDFORMING A DIFFUSION GAP FOR SUBSTANTIALLY SEALING SAID WORK CHAMBERRELATIVE TO SAID PROTECTIVE CHAMBER.